Triazolinediones as highly enabling synthetic tools

Triazolinediones (TADs) are unique reagents in organic synthesis that have also found wide applications in different research disciplines, in spite of their somewhat "exotic" reputation. In this review, we offer two case studies that demonstrate the possibilities of these versatile and reliable synthetic tools, namely, in the field of polymer science as well as in more recently emerging applications in the field of click chemistry. As the general use of triazolinediones has always been hampered by the limited commercial and synthetic availability of such reagents, we also offer a review of the available TAD reagents, together with a detailed discussion of their synthesis and reactivity. This review thus aims to serve as a practical guide for researchers that are interested in exploiting and further developing the exceptional click -like reactivity of triazolinediones in various applications

Polymerization of metallocene-catalyzed long-chain branched and functional polypropylene

Propylene was polymerized with homogeneous and heterogeneous metallocene catalysts. In addition to homopolymerizations, copolymerizations were conducted with α-olefins, dienes and functional comonomers. Propylene/1,9-decadiene copolymers were polymerized with racemic dimethylsilanylbis(2-methyl-4-phenyl-1-indenyl)zirconium dichloride supported on methylaluminoxane-modified silica. Rheological tests showed long-chain branching in the copolymers, even with comonomer incorporations of less than 1 mol %. Hydroxyl functional propylene/10-undecen-1-ol copolymers were polymerized with homogeneous racemic dimethylsilanylbis(2-methyl-4-phenyl-1-indenyl)zirconium dichloride. Addition of triisobutylaluminum eliminated the drop in molecular weight with increasing comonomer content, and the interactions between the active center and the hydroxyl group at the end of the comonomer chain were more efficiently blocked. Catalyst activity was improved by increase in the proportion of methylaluminoxane in the cocatalyst mixture. Functionality contents up to 2 mol % were obtained by lowering pressure. The functional polypropylene exhibited significantly enhanced peel strength and paintability relative to a reference homopolypropylene. Adhesion properties were improved not only in the copolymer but also in a blend consisting of propylene homopolymer and functional polypropylene, even when functionality content was only 0.17 wt %. The functional polypropylene slightly increased the adhesion between polypropylene and polyamide phase or silica filler, although the effect on impact strength was not as good as desired. In copolymerization with metallocene catalysts, the comonomer distribution is uniform along the polypropylene backbone and the stereospecificity is maintained. The properties of the polypropylene are dramatically affected even with comonomer incorporations less than 1 mol %, regardless of whether the comonomer is a non-conjugated diene to induce long-chain branching or contains a functional group to improve adhesion properties.reviewe

Advances in PNP-ligated rare-earth-metal complexes: Reactivity and catalytic performances

Due to the large ionic radius and high electro-positivity nature, rare earth metal complexes are difficult to stabilize and undergo pathways like ligand redistribution and intramolecular C-H activation. To solve such problems and retain reactive versatility, rare earth complexes supported by a variety of tridentate PNP pincer ligands have been explored. Such complexes can serve as perfect precursors for preparing ultra-active rare earth species containing two metal-carbon bands, let alone Ln=N and Ln=P multiple bonds. In addition, the combined stability and activity of the cation rare earth mediates made them the best catalysts for the polymerization of olefins and other non-polar hydrocarbon monomers, especially conjugated dienes. The practical utilization of rare earth metal catalysts for new materials production have also extensively explored by experts from the academic and industries

Magic of alpha : the chemistry of a remarkable bidentate phosphine, 1,2-bis(di-tert-butylphosphinomethyl)benzene

We thank the Fonds der Chemischen Industrie for a Kekulé Fellowship for a studentship and the Deutsche Forschungsgemeinschaft (DFG, project number 424535516) for support (J.V.). We are also very grateful to Lucite International for funding the work in St Andrews that is contained in this review.The bidentate phosphine ligand 1,2-bis(di-tert-butylphosphinomethyl)benzene (1,2-DTBPMB) has been reported over the years as being one of, if not the, best ligands for achieving the alkoxycarbonylation of various unsaturated compounds. Bonded to palladium, the ligand provides the basis for the first step in the commercial (Alpha) production of methyl methacrylate as well as very high selectivity to linear esters and acids from terminal or internal double bonds. The present review is an overview covering the literature dealing with the 1,2-DTBPMB ligand: from its first reference, its catalysis, including the alkoxycarbonylation reaction and its mechanism, its isomerization abilities including the highly selective isomerizing methoxycarbonylation, other reactions such as cross-coupling, recycling approaches, and the development of improved, modified ligands, in which some tert-butyl ligands are replaced by 2-pyridyl moieties and which show exceptional rates for carbonylation reactions at low temperatures.PostprintPeer reviewe

Synthesis, characterization, and reactivity of organometallic complexes of early and late metals and the functionalization of polydienes

A series of rhodium and iridium organometallic complexes supported by 1-cyclopentadienyl-1,1-bis(4,4-dimethyl-2-oxazolinyl)ethane (MeC(OxMe2)2(C5H4); BoMCp) and 1-fluorenyl-1,1-bis(4,4-dimethyl-2-oxazolinyl)ethane (MeC(OxMe2)2(C13H8); BoMFlu) are described. Metalation of BoMCp readily occurred through salt metathesis from a thallium intermediate or protonolysis with appropriate metal precursors. In contrast, metalation of the more basic BoMFlu ligand required in situ generation of a potassium carbanion with potassium benzyl and salt metathesis with appropriate metal precursors. The piano-stool complexes of BoMCpM (M = Rh or Ir) were unreactive to substitution chemistry and forcing condition required for C–H activation reactions resulted in decomposition of catalysts prior to successful reactions. However, the two-electron oxidation of BoMCpRh(C2H4)2 with Br2 results in BoMCpRhBr2, a new RhIII species. BoMFluM (M = Rh or Ir) complexes readily underwent substitution chemistry. In addition, BoMFluRhL2 (L2 = C8H12 or C16H12) displayed unique electrochemistry of two reversible 1-electron oxidations. The RhII species could be generated in solution with life time greater than 24 hours for L2 = C16H12. A series of lanthanide organometallic complexes, Ln{C(SiHMe2)3}3 (Ln = La, Ce, Pr, Nd) were activated by the abstraction of Si–H with 1 and 2 equivalents B(C6F5)3 to generate Ln{C(SiHMe2)3}2HB(C6F5)3 and Ln{C(SiHMe2)3{HB(C6F5)3}2 respectively. The addition of AlR3 (R = Me or iBu) to Ln{C(SiHMe2)3}3 resulted in the complexation of the weaker lewis acid rather than Si–H abstraction. The hydridoborate alkyl complexes, with AliBu3 co-catalysts, are active in butadiene polymerization. Neodymium and cerium were shown to be the most active and all lanthanides showed a ~50:50 selectivity for cis-1,4:trans-1,4 insertions, with exception of lanthanum which showed a slightly higher selectivity for trans-1,4. Further studies with precatalysts Nd{C(SiHMe2)3}3 indicate a polymerization with living character with respect to reaction time but also showed a dependence of molecular weight on Nd:AliBu3 ratio supporting the proposed chain transfer mechanism. Polymerization in saturated hydrocarbon solvent (heptane) improved cis-1,4 selectivity to nearly 90% with Nd{C(SiHMe2)3}3 pre-catalyst. Nd{C(SiHMe2)3{HB(C6F5)3}2 with 10 equivalents AliBu3 was \u3e95% selective in the polymerization of isoprene to cis-1,4 polyisoprene with good activity in toluene. In contrast, Nd{C(SiHMe2)3}2HB(C6F5)3 was less active in the polymerization of isoprene and displayed a lower selectivity yielding ~40% trans-1,4 polyisoprene. The activation of Nd{C(SiHMe2)3}3 in toluene with different protocols containing the organochloride Ph3CCl were also successful for cis-1,4 selective polymerizations of isoprene. In addition, activation protocols with Ph3CCl improved the cis-1,4 selectivity of polybutadiene to 90% and above. Attempts to utilize Ph3CCl based activations in heptane resulted in highly reactive polymerization ultimately isolating gelled polybutadiene. Functionalizing agents for the functionalization of polydienes were synthesized from modified literature procedures. The modifications allowed for higher yields for compounds such as (EtO)3Si-CC-Si(OEt)3. The application of (EtO)3Si-CC-Si(OEt)3 as a quenching agent for neodymium-based diene polymerizations resulted in the incorporation of silyl functionalized polydiene and improved physical properties of the resulting rubber composites. 2-Me2XSi-1,3-C4H5 (X = OiPr, OtBu, and NiPr2) monomers were also synthesized and studied for the functionalization of polydienes. No functional group incorporation during neodymium-based polymerizations was observed for X = OiPr or OtBu. However, when X = NiPr2 SiMe groups were observed to be incorporated into polydienes indicating successful functionalization

Studies on Stereospecific Polymerization of Polar Monomer with Zirconium Complexes

埼玉大学博士(理学)100 p.Chapter 1 General Introduction 7 Chapter 2 Isospecific Polynerization of ω-alken-α-oxytriisopropylsilane with zirconium complex with [OSSO]-type ligard 37 2-1 Introduction 38 2-2 Polymerization of siloxy-substituted α-olefin 40 2-3 Conclusion 52 2-4 Experimental Section 53 2-5 Reference 55 Chapter 3 Copolymerization of 5-hexen-l-oxytriisoropylsilane with ethylene or l-hexene catalyzed by zirconium complex having[OSSO]-type ligard 58 3-1 Introduction 59 3-2 Copolymerization of ethylene with 5-hexen-l-oxytriisoropylsilane 61 3-3 Copolymerization of 1-hexene with 5-hexen-l-oxytriisoropylsilane 73 3-4 Conclusion 78 3-5 Experimental Section 79 3-6 Reference 81 Chapter 4 Transformation of the terminal siloxy-substituted poly(α-olefin)s 82 4-1 Introduction 83 4-2 Transformation of siloxy-substituted polymer into acetoxy-substituted polymer 85 4-3 Conclusion 91 4-4 Experimental Section 92 4-5 Reference 94 Chapter 5 Couclusion and Outlook 95 Acknowledgement 98 List of Publications 100指導教員 : 石井昭彦textapplication/pdfdoctoral thesi

Development of new olefin metathesis reactions via substrate modification: Alkyne and olefin metathesis

학위논문 (박사)-- 서울대학교 대학원 : 화학부 유기화학 전공, 2016. 2. 최태림.Olefin metathesis (OM) reaction is a facile reaction to synthesize various molecules through carbon-carbon double bond rearrangement. With the development of more reactive yet functional group tolerant catalysts, OM proved its usefulness and became one of the most important reaction in modern organic chemistry. Among the various olefins that can subjected to OM, alkynes have special characteristic. As OM only exchanges carbon-carbon double bonds, reaction between alkyne and metal carbene catalyst does not completely cleave carbon-carbon triple bond: instead, new metal 1,3-dienylidene is formed, which can undergo further metathesis reactions, such as enyne metathesis or conjugated polyene synthesis. This thesis will describe about the various application of OM with alkynes, from synthesis of small molecules to high-molecular-weighted conjugated polyenes. Chapter 2 describes synthesis of multicyclic compounds through selective tandem dienyne ring-closing metathesis (RCM) reaction and Diels-Alder reaction. Dienyne RCM reaction is a useful reaction to synthesize fused bicyclic compounds, but due to the lack of catalyst selectivity between olefins with same structures, dienyne RCM reaction tend to produce two different isomers with different ring sizes. Also, product of conventional dienyne RCM reaction was restricted to the bicyclic compounds containing small or medium sized rings only. Thus, conformation of 1,3-diene functional group in bicyclic compound was fixed to s-trans conformation, thus further modification such as Diels-Alder reaction was impossible. By modifying the dienyne substrate to contain long tether to synthesize bicyclic compound comprising small (5-7 membered) and large (14-17 membered) rings, both problems could be solved. As cyclization rate of small ring and catalyst exchange rate between alkenes were significantly faster than that of large ring, single isomer could be synthesized from dienyne RCM reaction. Also, due to the flexible macrocycle chain, 1,3-diene functional group could form s-cis conformation, which could undergo Diels-Alder reaction to synthesize multicyclic compound. Chapter 3 describes tandem ring-opening/ring-closing metathesis (RO/RCM) polymerization of monomers containing cycloalkene and alkyne. Although cycloalkenes with low ring strain and alkynes were not suitable for metathesis polymerization, mixing those two functional groups in one monomer facilitated efficient tandem RO/RCM reaction to perform ultrafast living polymerization. Living characteristic of tandem polymerization could also synthesize block copolymers. Also, 1,3-diene functional groups in the polymer backbone could undergo further modification by cycloadditionr reactions. By changing monomer structures, we found out that monomers with certain combinations of cycloalkene, alkyne, and linker group could undergo efficient polymerization, while monomers with other combinations did not. In order to increase polymerization efficiency, two strategies were proposed. Firstly, monomer structures were modified to increase intramolecular RO/RCM with enhanced Thorpe-Ingold effect, which allowed the synthesis of challenging dendronized polymer. Secondly, reaction concentration was reduced to suppress intermolecular side reactions, which could effectively polymerize monomers without structural modifications. In order to further broaden the monomer scope, monomers containing internal alkynes were also studied, and surprisingly, monomers with internal alkynes tend to undergo non-selective α- and β-addition to form two different polymer units with different ring structures. Further studies revealed that steric and electronic effects of internal alkyne substituents changed polymer unit ratio, polymerization reactivity, and even polymerization kinetics. Thorough mechanism study revealed that the rate-determining step of monomers containing certain internal alkyne was six-membered ring cyclization step via β-addition, whereas that for monomers containing other alkynes was the conventional intermolecular propagation step, as observed in other chain-growth polymerization reactions. Last chapter describes about fast cyclopolymerization of 1,7-octadiyne derivatives. Although cyclopolymerization was effective for the synthesis of conjugated polyenes, cyclopolymerization of 1,7-octadiyne was rarely studied, due to the slow polymerization rate by slow six-membered ring cyclization rate. Although this polymerization rate could be increased by using bulky substituents in side chains, simply increasing substituent bulkiness could not effectively increase polymerization rate. Thus, we proposed two strategies to increase polymerization rate. Firstly, dimethyl substitution was introduced to α-position of side chains. This strategy effectively increased polymerization rate by enhanced Thorpe-Ingold effect, and synthesis of 50-mer polymer could be done within 1 hour, instead of previous 24 hours. However, in order to achieve controlled polymerization, reaction temperature should be decreased and polymerization time was increased to 6 hours. To solve this problem, second strategy was applied: by changing substituent position from 4,4-disubstitution to 4,5-disubstitution, polymerization rate was significantly increased, and even living polymerization with narrow PDI and well-predictable molecular weight was possible within 1 hours, and even challenging synthesis of dendronized polymer could be possible. All those polymers were analyzed by UV-Vis, NMR, and IR spectroscopy to observe polymer backbone structures, such as conjugation length of polymer and cis/trans conformation of polymer backbone.Chapter 1. Olefin metathesis reaction with alkyne 1 Brief history of olefin metathesis with alkyne 3 Thesis research 9 References 10 Chapter 2. Synthesis of fused multicyclic compound through dienyne ring-closing metathesis and Diels-Alder reaction 13 Abstract 15 Background 15 Introduction 18 Results and Discussions 19 Conclusion 35 References 36 Chapter 3. Tandem ring-opening/ring-closing metathesis polymerization 39 Abstract 41 Background 42 Part A. Tandem RO/RCM of monomers containing nitrogen linker group 45 Introduction 45 Results and Discussions 46 Conclusion 61 Part B. Strategies and deeper mechanistic study of monomers with low reactivity 62 Introduction 62 Results and Discussions 62 Conclusion 82 References 83 Chapter 4 Fast diyne cyclopolymerization of 1,7-octadiynes 87 Abstract 89 Backgrounds 89 Part A. Cyclopolymerization of 1,7-octadiynes containing dimethyl substituents in α-position of side chain 93 Introduction 93 Results and Discussions 95 Conclusion 104 Part B. Cyclopolymerization of 4,5-disubstituted 1,7-octadiyne 106 Introduction 106 Results and Discussions 107 Conclusion 120 References 120 Supporting Information 123 국문 초록 135Docto

Natural Polymers and Biopolymers II

BioPolymers could be either natural polymers – polymer naturally occurring in Nature, such as cellulose or starch…, or biobased polymers that are artificially synthesized from natural resources. Since the late 1990s, the polymer industry has faced two serious problems: global warming and anticipation of limitation to the access to fossil resources. One solution consists in the use of sustainable resources instead of fossil-based resources. Hence, biomass feedstocks are a promising resource and biopolymers are one of the most dynamic polymer area. Additionally, biodegradability is a special functionality conferred to a material, bio-based or not. Very recently, facing the awareness of the volumes of plastic wastes, biodegradable polymers are gaining increasing attention from the market and industrial community. This special issue of Molecules deals with the current scientific and industrial challenges of Natural and Biobased Polymers, through the access of new biobased monomers, improved thermo-mechanical properties, and by substitution of harmful substances. This themed issue can be considered as collection of highlights within the field of Natural Polymers and Biobased Polymers which clearly demonstrate the increased interest in this field. We hope that this will inspire researchers to further develop this area and thus contribute to futures more sustainable society.